Section 1 - Introduction.pdf

Section 1

Introduction to Stimulation Table of Contents Introduction................................................................................................................................................1-3 How This Course is Organized ..............................................................................................................1-3 Study Suggestions ..................................................................................................................................1-4 The Purpose of Stimulation in an Oil Well................................................................................................1-5 Delivering Quality and Value.................................................................................................................1-5 Halliburton and the Drilling of an Oil Well ...............................................................................................1-6 Drilling Operations.................................................................................................................................1-6 Running Drill Pipe .................................................................................................................................1-6 Running Surface Casing.........................................................................................................................1-7 Cementing ..............................................................................................................................................1-8 Tripping In............................................................................................................................................1-10 Running and Cementing Intermediate Casing......................................................................................1-10 Drilling To Final Depth........................................................................................................................1-10 Completing the Well ............................................................................................................................1-10 Setting Production Casing ....................................................................................................................1-11 Perforating............................................................................................................................................1-11 Installing the Completion System ........................................................................................................1-12 Sand Control.........................................................................................................................................1-12 Installing the Christmas Tree ...............................................................................................................1-12 Acidizing ..............................................................................................................................................1-13 Fracturing .............................................................................................................................................1-13 Historical Background of Stimulation .....................................................................................................1-14 History of Acidizing.............................................................................................................................1-14 History of Hydraulic Fracturing ...........................................................................................................1-14 Halliburton Energy Services Vision and Mission....................................................................................1-16 HES 2003 Vision Statement.................................................................................................................1-16 Production Enhancement Vision and Guiding Principles ....................................................................1-16 HES Mission Statement .......................................................................................................................1-17 General Safety and Work Guidelines.......................................................................................................1-18 Stimulation Job Descriptions (Frac/Acid)................................................................................................1-20 Oilfield Terms, Slang, and Acronyms .....................................................................................................1-22 Common Oilfield Terms ......................................................................................................................1-22 Common Oilfield Acronyms ................................................................................................................1-35 Common Halliburton Acronyms ..........................................................................................................1-38 Unit A Quiz ..........................................................................................................................................1-40 Answer Key .............................................................................................................................................1-41

1•1 © 2005, Halliburton

Stimulation I

Introduction to Stimulation

Use for Section notes…

© 2005, Halliburton

1•2

Stimulation I

Introduction to Stimulation

Introduction Welcome to Halliburton’s Production Enhancement (PE) Product Service Line (PSL). Halliburton is the world leader in oil and gas well stimulation, both in market position and customer perception. Consistently ranked number one in value by independent surveys of oil and gas customers, the Production Enhancement PSL provides excellent value for oil and gas operators throughout the world. Halliburton helped to pioneer well fracturing back in 1949.

your enrollment and can assist you in completing the course.

Halliburton's PE PSL encompasses the technologies and capabilities to optimize hydrocarbon reservoir performance through a variety of approaches generally based on pressure pumping services. The PSL’s reservoir focus drives technology development in fluids, materials, and equipment. Included in the PE PSL are Stimulation (fracturing and acidizing), Sand Control, Coiled Tubing, Well Control / Hydraulic Workover (HWO), Nitrogen Services, and Pipeline and Process Services. This course primarily covers only Stimulation.

Each section in this workbook contains several units. Each unit contains all the information you need. Other manuals or catalogs are not necessary, with the possible exception of a Red Book and dictionary. Each unit is made up of text, figures to help explain the text (pictures, drawings charts, etc.), and a unit quiz. When you complete all the units in a section, you complete a self-check test. Both the quizzes and tests will help you check your personal progress. The time you spend on each unit is not important; it is important that you learn and retain the content.

This course is your introduction to the well stimulation process: what it is, why is it done, and how we do it. From this course, you will learn many new terms, types of equipment, types of materials, and processes. By completing this course, you will be able to more effectively communicate with others in the PSL and at the job site, be better able to participate in stimulation jobs, and be prepared to take on more responsibility. You will start to become an invaluable person who can deliver the Customer Service that has been a Halliburton tradition for more than 80 years.

At the end of every section are the answers to all unit quizzes and the self-check tests. After you complete a quiz or a test, refer to the appropriate answer key. Let your supervisor know when you complete a section. Then you will take a written test that is graded. This section test is based solely upon the information in your workbook. However, you cannot use your workbook as a reference while taking the test.

How This Course is Organized Familiarize yourself with the way this workbook is organized. You will find a table of contents at the beginning of each section, followed by an introduction, a list of topic areas, and the learning objectives for that section.

Successful completion of all the section tests and a comprehensive final examination makes you eligible to attend the next level course. For more information on a subject covered in your workbook, let your resource personnel know of your interest — they can direct you to more information.

Take time to carefully read this introduction. It will acquaint you with this course and suggest ways to get the most out of it. This workbook allows you to learn at your own speed, without an instructor, and at any time or place that may be convenient for you. Your immediate supervisor is normally responsible for

© 2005, Halliburton

1•3

Stimulation I

Introduction to Stimulation

•

Study Suggestions This course was planned to make learning as easy as possible. However, to retain the knowledge, you must put forth effort. Remember, the responsibility for learning this course is yours.

When you work through all the units in a section, you will be ready to take the self-check test for that section. Go back through all the units to review what you have learned. Your completed unit quizzes should also be helpful here.

Keep your workbook available at all times; you never know when you might have the opportunity to work on a unit. Try and set aside enough time to complete an entire unit during a study period. Some study suggestions include •

Review both the section and unit introductions. They will very briefly describe what is in the unit.

•

Skim through the unit. Look at the figures and headings to see what's familiar to you and what isn't. They will tell you what to expect.

•

Read the content carefully. Go back to the beginning of the unit and read the content, paragraph by paragraph. Study the figures. If you are unfamiliar with the meaning of a word, look it up in a dictionary.

•

Check your understanding. Try to put into your own words the paragraph you have just read. Go back and underline or make notes of important points. This will help you to review the content of the unit later.

•

Review the unit. At the end of each unit, take a few minutes to look over your notes.

•

Take the unit quiz. Try not to refer to the text when you are filling in the blanks in the unit quiz. Write your answers in your workbook.

© 2005, Halliburton

Check your answers against the answer key. Reread the parts of the text that relate to the items you are unsure about or you have answered incorrectly. Don't forget, if you are having trouble, or if you feel your response is equally correct, consult your resource personnel.

If you are having trouble choosing or calculating an answer, go to the next question. At the end of the test, go back to the questions you didn't answer and try again. Remember, you are not competing with anyone but yourself. Take your time and do your best. When you finish a self-check test, turn to the answer key at the end of the section to check your answers. References are provided as to where the answers can be found. Make sure that you understand the correct answers before proceeding to another section. Check with your resource personnel if you feel the response you gave is correct. Don't forget to let your program coordinator know that you have completed the section. Upon completion of a section, ask your supervisor any questions you might have before taking the in-class section test. Successful completion of the test enables you to move on to the next section. Remember that successful completion of all in-class section tests and the comprehensive course final examination enables you to be enrolled in the appropriate next level school.

1•4

Stimulation I

Introduction to Stimulation

The Purpose of Stimulation in an Oil Well After an oil or gas well is drilled, the wellbore pressure is reduced to less than the oil or gas bearing formation. This higher formation pressure forces the oil or gas to the wellbore, where it then travels to the surface. Sometimes, the flow of oil or gas (well production or productivity) is too small for the operator to make any profit. If the reservoir does contain enough oil or gas to make it commercially sufficient, then the problem may be formation damage near the wellbore caused during the drilling process or be a formation with low permeability (ability to allow flow). In either case, the flow needs to be stimulated.

•

Fluid type

•

Viscosity requirements

•

Fluid rheology

•

Fluid Safety

•

Economics of the fluid

•

Proppant selection

•

Material availability

•

Experience with local formations

•

Laboratory data on the formation

In fact, Halliburton tailors the treatment fluid specifically to the reservoir. The results are minimized damage and maximized results. Whether the application calls for linear gels, crosslinked gels, viscosified oils, or foam, we have the experience and knowledge to design, prepare, and carry out the stimulation operation.

Stimulation treatments include both acidizing and hydraulic fracturing. Acidizing refers to the use of acid pumped into the oil-bearing formation to dissolve parts of the formation so that oil (or gas) can flow more easily to the well. Hydraulic fracturing refers to pumping a fluid into the formation at sufficiently high pressures so that the formation rock actually cracks, again creating paths for the fluid to flow. These cracks may be further etched with acid or have a proppant (such as Ottawa sand) pumped into them to prop the cracks open after the pressure is released (Figure 1.1).

Delivering Quality and Value Halliburton’s challenge is to create an economical fluid that easily and safely transports the required proppant into the fracture. The fluid must then break and be recovered from the fracture, allowing the proppant pack to produce unimpeded by the placement fluid. Our solutions include the wide range of Fracturing Fluid Systems. Halliburton has long been the industry leader in giving the most value from the stimulation treatment by increasing hydrocarbon production from the formation. We must consider all of the design requirements necessary for a successful job including:

© 2005, Halliburton

Figure 1.1 - Stimulation increases the flow of oil or gas from the reservoir to the well.

1•5

Stimulation I

Introduction to Stimulation

Halliburton and the Drilling of an Oil Well To begin, an oil company (called an operating company or the operator, such as Shell, Texaco, or BP-Amoco) must locate areas where there is a good potential for hydrocarbons to be found (an oil or gas reserve). To do this, they examine the geology and conduct other tests (such as seismic) using Reservoir Engineers, Geologists, Geophysicists, and Petrophysicists from their own staff or using a contractor such as Halliburton’s Reservoir Description PSL. If the potential exists, the operator must then acquire the right to drill by buying or leasing the land.

How deep is the reservoir (the depth of an oil or gas well can range from a few hundred to more than 20,000 feet)?

•

What kind of pressures will be encountered?

•

What will be the cost?

•

How will the reservoir be controlled?

•

Will this well be profitable?

trip the drill string out of the hole to put on a new bit and running it back to bottom

•

help run and cement casing, which is steel pipe that is put into the hole at various, predetermined intervals.

Running Drill Pipe The drill bit is made up (screwed on) the bottom end of the first drill collar which is heavy wall pipe (Figure 1.2) Enough collars and drill pipe are made up and lowered in (called tripping in) until the bit is almost to bottom. Then, the kelly is attached. (kelly is a four- or six-sided piece of pipe that fits into the kelly bushing, which fits into the master bushing in the rotary table (Figure 1.3). The rotary table is the part of the derrick floor that spins the drill pipe. The system is like a wrench turning a bolt.) The drill string then starts to rotate and weight is applied to drill the hole. (The bit is allowed to contact the bottom of the hole.)

Drilling Operations Simply stated, the drilling rig crew’s normal drilling operations are to: keep a sharp bit on bottom, drilling as efficiently as possible

© 2005, Halliburton

•

For drilling to be effective, a special fluid (called drilling mud) must be used to carry away the drill cuttings and lubricate and cool the drill bit. The industry’s top provider of drilling fluids is Halliburton’s BAROID PSL. Also, Halliburton’s Security DBS PSL is one of the top providers of drilling bits. And if the well is to be drilled at an angle other than straight down (called a deviated well), a subcontractor with the specialized equipment and knowledge may be brought in, such as Halliburton’s Sperry-Sun Drilling Services.

The operator must also hire a service and supply company (such as Halliburton) to provide drilling mud and bits, casing and casing attachments, cementing, and measuring and testing services.

•

add a new joint of drill pipe as the hole deepens

Often, special casing crews are hired to run the casing, and usually a cementing company is called on to place cement around the casing to bond it in place in the hole. Still, the rig crew usually assists in casing and the cementing operation.

The operator will then hire a drilling contractor to actually drill the well (such as Parker Drilling or Santa Fe International). The operator may manage the whole drilling project or they may hire a contractor to manage it, such as Halliburton’s Integrated Solutions PSL. Before drilling can begin, the operating company must determine the following: •

•

1•6

Stimulation I

Introduction to Stimulation

casing, which is large in diameter and, like all casing, is nothing more than steel pipe and comes in 30- or 40-ft lengths (Figure 1.4). Running casing into the hole is very similar to running drill pipe, except that the casing diameter is much larger and thus requires special elevators, tongs, and slips to fit it. For example, in a 17 1/2-in. hole, 13 3/8-in. casing might be used.

Figure 1.2 - Drill bit.

Figure 1.4 - Casing.

Also, devices called centralizers and scratchers (Figure 1.5) are often installed on the outside of the casing before it is lowered into the hole. Centralizers are attached to the casing and, since they have a bowed-spring arrangement, keep the casing centered in the hole after it is lowered in. Centralized casing can be better cemented in the hole. Scratchers also help make better cement jobs by removing the wall cake formed by the drilling mud as the casing is moved up and down or rotated (depending on scratcher design) allowing the cement to better bond to the formation.

Figure 1.3 - Kelly, kelly bushing, and rotary table.

When near the end of the pipe, rotation is stopped and another section of pipe is attached. This continues until the desired depth is reached or the drill bit must be replaced. Then the drill pipe is picked up and disassembled (called tripping out), the new bit is attached, and the string is tripped back into the hole.

Other casing accessories include a guide shoe, a heavy steel and concrete piece attached to the bottommost joint of casing that helps guide the casing past small ledges or debris in the hole; and a float collar, a device with a valve installed in the casing string two or three joints from bottom. A float collar is designed to serve as a receptacle for cement plugs and to keep drilling mud in the hole from entering the casing as it is run into the hole. Just as a ship floats in water, casing floats in a hole full of mud (if mud is kept out of the casing). This buoyant effect helps

Running Surface Casing At predetermine times, the drill pipe is removed and the casing crew moves in to do its work. The first string of casing they run is called surface

© 2005, Halliburton

1•7

Stimulation I

Introduction to Stimulation

equipment to handle this material in bulk. Bulk cement storage and handling equipment is moved out to the rig, making it possible to mix large quantities of cement at the site. The cementing crew mixes the dry cement with water, using a recirculating mixer (Figure 1.6). The dry cement is gradually added to the tub, and a jet of water thoroughly mixes with the cement to make slurry (very thin, watery cement).

relieve some of the weight carried on the mast or derrick as the long string of heavy casing hangs suspended in the hole.

Figure 1.6 - Cement Recirculating Mixer (RCM).

Special pumps pick up the cement slurry and send it up to a valve called a cementing head (also called a plug container) mounted on the topmost joint of casing that is hanging in the mast or derrick a little above the rig floor (Figure 1.7). Just before the cement slurry arrives, a rubber plug, called the bottom plug (Figure 1.8), is released from the cementing head and precedes the slurry down the inside of the casing. The bottom plug stops or “seats” in the float collar, but continued pressure from the cement pumps opens a passageway through the bottom plug (by rupturing a diaphragm). Thus, the cement slurry passes through the bottom plug and continues on down the casing. The slurry then flows out through the opens in the guide shoe and starts up the annular space between the outside of the casing and wall of the hole. Pumping continues and the cement slurry fills the annular space.

.

Figure 1.5 – Scratcher and centralizer

Cementing

A top plug, which is similar to the bottom plug except that it is solid, is released as the last of the cement slurry enters the casing. The top plug follows the remaining slurry down the casing as displacement fluid (usually water or drilling mud) is pumped in behind the top plug. Meanwhile, most of the cement slurry flows out

After the casing string is run, the next task is for Halliburton to cement the casing in place. As when casing is run, the rig crew is available to assist. Halliburton stocks various types of cement and cement additives and has special transport

© 2005, Halliburton

1•8

Stimulation I

Introduction to Stimulation

of the casing and into the annular space. By the time the top plug seats on or “bumps” the bottom plug in the float collar, which signals (by an increase in pressure) the cementing pump operator to shut down the pumps, the cement is only in the casing below the float collar and in the annular space. Most of the casing is full of displacement fluid.

Figure 1.8 - Top and bottom plugs for cementing.

Figure 1.7- Plug container

After the cement is run, a waiting time is allotted to allow the slurry to harden. This period of time is referred to as waiting on cement (WOC). After the cement hardens, tests may be run to ensure a good cement job. After the WOC and tests indicate that the job is good, the rig crew attaches or nipples up the blowout preventer (BOP) stack to the top of the casing (Figure 1.9). The BOP stack is pressure-tested, and drilling is resumed with a smaller bit that fits inside the surface casing. Figure 1.9 - Blowout preventer (BOP).

© 2005, Halliburton

1•9

Stimulation I

Introduction to Stimulation

such as 7 7/8-in. for our example. This bit is tripped in, drills out the intermediate casing shoe, and heads toward what everyone hopes is a pay zone, which is a formation capable of producing enough oil and/or gas to make it economically feasible for the operating company to complete the well.

Tripping In To resume drilling, a smaller bit is selected, because it must pass down inside the surface casing. To drill the surface hole, the example rig crew used a 17-1/2 inch bit, whereas a 12-1/4 inch bit will now be used. In this case, the outside diameter of the surface casing is 13-3/8 inches, so in order to get adequate clearance, a 12-1/4 inch bit is used. As before, the bit is made up on the drill collars followed by drill pipe.

Once again several bits will be dulled and several round trips will be made, but before long the formation of interest (the pay zone, the oil sand, or the formation that is supposed to contain hydrocarbons) is penetrated by the hole. It is now time for a big decision. The question is, “Does this well contain enough oil or gas to make it worthwhile to run the final production string of casing and complete the well?”

Running and Cementing Intermediate Casing At this point, particularly in deep wells, another, smaller diameter string of casing may be set and cemented in the hole, such as using a 12 1/4-in. bit and 8 5/8-in. casing. This casing string is the intermediate string. It runs all the way from the surface, down through the surface casing, and to the bottom of the intermediate hole. Sometimes intermediate string is needed in deeper holes because there are almost always so-called troublesome formations are encountered in the hole.

Completing the Well After careful consideration of the data obtained from tests run on the formation or formations of interest a decision is made on whether to set production casing and complete the well or “plug and abandon” it (PTA). If the decision is to abandon it, the hole is considered to be dry, that is, not capable of producing oil or gas in commercial quantities. In other words, some oil or gas may be present but not in amounts great enough to justify the expense of completing the well.

Troublesome formations are those that may contain formation fluids under high pressure and, if not sealed off by casing and cement, could blow out, making it difficult if not impossible to eventually produce oil or gas from the well. Or perhaps there is sloughing shale, a formation composed of rock called shale that swells up when contacted by the drilling mud and falls or sloughs off into the hole. Many types of troublesome formations can be overcome while they are being drilled but are better cased off and cemented prior to drilling the final portion of the hole.

Therefore, several cement plugs will be set in the well to seal it off (Figure 1.10). However, sometimes wells plugged and abandoned as dry at one time in the past may be reopened and produced if the price of oil or gas has become more favorable. The cost of plugging and abandoning a well may only be a few thousand dollars. Contrast that cost with the price of setting a production string of casing --$50,000 or more. Therefore, the operator’s decision is not always easy.

Drilling To Final Depth Whether intermediate casing is set or not, the final part of the hole is what the operating company hopes will be the production hole. To drill it, the crew makes up a still smaller bit,

© 2005, Halliburton

1 • 10

Stimulation I

Introduction to Stimulation

Perforating Because the pay zone is sealed off by the production string and cement, perforations must be made in order for the oil or gas to flow into the wellbore. Perforations are simply holes that are made through the casing and cement and extend some distance into the formation. The most common method of perforating incorporates shaped-charge explosives (similar to those used in armor-piercing shells). Figure 1.10 - Cement used to plug a well.

Setting Production Casing If the operating company decides to set casing, casing will be brought to the well and for one final time, the casing and cement crew run and cement a string of casing. Typically, the production casing is set and cemented through the pay zone; that is, hole is drilled to a depth beyond the producing formation, and the casing (5 ½-in. for our example) is set to a point near the bottom of the hole. As a result, the casing and cement actually seal off the producing zone--but only temporarily. After the production string is cemented, the drilling contractor has almost finished his job except for a few final touches.

Figure 1.12- Perforating gun: (A) gun in hole, (B) gun firing, and (C) oil flowing through perforations.

Shaped charges accomplish penetration by creating a jet of high-pressure, high-velocity gas (the leading supplier is Halliburton’s Jet Research Center). The charges are arranged in a tool called a gun that is lowered into the well opposite the producing zone. The gun can be lowered on wireline or tubing. When the gun is in position, the charges are fired by electronic means from the surface (Figure 1.12). After the perforations are made, the tool is retrieved. Perforating is usually performed by a service company that specializes in this technique, such as Halliburton’s Logging & Perforating PSL or Tools, Testing, and TubingConveyed Perforating (TT&TCP) PSL.

Conductor Casing Cement Surface Casing

Intermediate Casing

Cement

Production Casing

Reservoir Cement

Casing Shoe

Figure 1.11- Schematic of casing and cement in well.

© 2005, Halliburton

1 • 11

Stimulation I

Introduction to Stimulation

Installing the Completion System

•

disposal and removal of formation sand

•

casing damage from compressive loading caused by subsidence

Halliburton’s Completion Products and Services PSL provides specialized surface and downhole equipment including gravel pack packers and screens to inhibit the movement of formation sand into the wellbore, surface pumping equipment, and filtration systems.

Even though the oil or gas can flow into the casing after it is perforated, usually, the well is not produced through the casing. Instead, smaller diameter pipe called production tubing is placed in the well to serve as a way for the oil or gas to flow to the surface. The tubing is run into the well with a packer installed at or near the end of the tubing. The packer is placed at a depth just above the producing zone. When the packer is expanded, it grips the wall of the production casing and forms a seal in the annular space between the outside of the tubing and the inside of the casing. Thus, as the produced fluids flow out of the formation through the perforations, they are forced to enter the tubing to get to the surface. Additional devices are placed in the well or in the production tubing string to control and monitor the fluid flow, such as subsurface safety valves and flow control equipment, surface safety systems, packers and specialty completion equipment, production automation, and well screens. Halliburton’s Completion Products and Services PSL can supply all these products.

Sand Control

Figure 1.13 - Production tubing with screen and gravel pack in place.

At times, the producing zone may also produce formation sand as well as the oil or gas. A screen may be attached to the end of the production tubing to help keep the sand out. Often, when a screen is used, gravel is also placed in the hole around the screen, which is known as a gravel pack (Figure 1.13).

Installing the Christmas Tree When casing is set, cemented, and perforated and when the tubing string is run, then a collection of valves called a Christmas tree is installed on the surface at the top of the casing (Figure 1.14). The tubing in the well is suspended from the tree, so as the well's production flows up the tubing, it enters the tree. As a result, opening or closing valves on the Christmas tree can control the production from the well. Usually, after the Christmas tree is installed, the well is said to be complete.

Formation sand can present a major obstacle to well production. The petroleum industry spends millions of dollars each year to prevent and repair sand control problems including •

reduced production rates

•

sand bridging in tubing and casing

•

erosion of downhole and surface equipment

© 2005, Halliburton

1 • 12

Stimulation I

Introduction to Stimulation

Fracturing When sandstone rocks contain oil or gas in commercial quantities but the permeability is too low to permit good recovery (or the formation has been damaged), a process called fracturing may be used to increase conductivity to a practical level. To fracture a formation, a fracturing service company (such as Halliburton’s Production Enhancement PSL) pumps a specially blended fluid down the well and into the formation under great pressure. Pumping continues until the formation literally cracks open. Meanwhile, sand or man-made granules, called proppants (Figure 1.15), are mixed into the fracturing fluid. The proppant enters the fractures in the formation, and, when pumping is stopped and the pressure released, the proppant remains in the fractures. Because the fractures try to close back together after the pressure is released, the proppant is needed to hold or prop the fractures open. These propped-open fractures provide passages for oil or gas to flow into the well.

Figure 1.14 - Christmas tree.

Acidizing Sometimes, petroleum exists in a formation but is unable to flow readily into the well because the formation has very low permeability (capability for fluid flow). If the formation is composed of rocks that dissolve when contacted by acid, such as limestone or dolomite, then a technique known as acidizing may be required. Acidizing is usually performed by an acidizing service company (such as Halliburton’s Production Enhancement PSL) and may be done before the rig is moved off the well; or it can also be done after the rig is moved away. In any case, the acidizing operation basically consists of pumping anywhere from fifty to thousands of gallons of acid into the well. The acid travels down the tubing, enters the perforations, and contacts the formation. Continued pumping forces the acid into the formation where it dissolves channels that provide a way for the formation's oil or gas to enter the well through the perforations.

© 2005, Halliburton

Figure 1.15 - Sand, which can be used as a proppant.

1 • 13

Stimulation I

Introduction to Stimulation

Historical Background of Stimulation The first attempts at stimulation occurred in the 1890s when nitroglycerin was used to stimulate hard rock wells in the northeastern states. The concept here was to fracture (rubbilize) the production interval in the near wellbore region to increase production rates. Although quite hazardous, this technique was extremely successful for increasing oil, gas, and water production.

the Dow Well Service Group. Halliburton Oil Well Cementing Co., began acidizing oil wells commercially in March of 1935.

History of Acidizing

History of Hydraulic Fracturing

Acidizing must be considered one of the oldest stimulation techniques still in modern use. Earliest records indicate that the first acid treatments were probably performed in 1895. Herman Frasch, a chief chemist at Standard Oil Company’s Solar Refinery at Lima, Ohio, is credited with having invented the technique.

The first attempts at hydraulic fracturing were made in 1947 in the Hugoton gas field in Grant County, Kansas, using Napalm thickened gasoline followed by a gel breaker. The results were not good, but the concept was introduced in a paper written by J.B. Clark of Stanolind in 1948. In 1949 the process was patented and Halliburton was given an exclusive license on the new process.

The ability of pressure to part or fracture the formation was recognized during these first acid stimulation treatments of the 1930s. It was noted that acid would etch the faces of the fracture, thereby not allowing for complete closure.

The first acidizing patent, issued to Frasch on March 17, 1896, involved a reagent (hydrochloric acid) that would react with limestone to produce soluble products. These soluble products were then produced from the formation with the well fluids. Although successful, for some unknown reason the use of acid declined and no evidence of acidizing is available during the ensuing 30 years.

The first two commercial fracturing attempts were performed on March 17, 1949 in Stephens County, Oklahoma (Figure 1.16) and Archer County, Texas. These treatments were completed using lease crude or a blend of crude and gasoline and about 100 to 150 lb of sand. Due to the outstanding results of these first two attempts, using hydraulic fracturing as a means of increasing production grew rapidly across the US to the point where 3000 jobs per month were being completed in the mid 1950s.

Many have described the modern era of acidizing which began in 1932 with discussions between Pure Oil Co. and the Dow Chemical Co. Pure had oil wells in the same area of Michigan as Dow’s brine wells. Pure’s geologist, W. A. Thomas, and John Grebe, who was in charge of Dow’s Physical Research Laboratory, suggested well productivity of a limestone formation could be improved with an acid treatment. Pure chose a test site and on February 11, 1932 the well was treated with 500 gallons of hydrochloric acid. Subsequently, Dow formed a new subsidiary on November 19, 1932 to handle the growing acidizing business. The subsidiary takes its name, Dowell Inc., from

© 2005, Halliburton

In the 10 years that followed, more than 1.2 billion pounds of sand were pumped into wells within the United States as acceptance grew for what has become one of the industry's most outstanding well stimulation techniques. In the early days of fracturing, a "big" job may have involved 2,000 gal of fluid and 1,000 lb of proppant. 25 years after the first fracturing jobs, treatments averaged about 37,000 gal of fluid and 45,000 lb of proppant. Today, jobs with

1 • 14

Stimulation I

Introduction to Stimulation

fracturing may also be used to help overcome wellbore damage, aid in secondary recovery operations, and help inject and dispose of brine and industrial wastes.

500,000 gal of fluid and one million pounds of proppant are not uncommon (Figure 1.17).

With the advancement of computer technology, field engineers can now use hydraulic fracture design simulators on the job site for more than just research purposes. These simulators require rock mechanic properties, fluid properties, treatment data, and economic data as inputs to calculate the most effective frac design. PreFrac data acquisition has become more sophisticated and varied in recent years because of new tools and technology. In-situ rock stresses, fracture orientation, fracture closure pressure, fluid efficiency, treatment pressure, and many other parameters can be determined through pre-frac treatment methods.

Figure 1.16 - One of the first two hydraulic fracturing jobs, this one performed in Stephens County, Oklahoma.

Two valuable aids to well stimulation became available with the introduction of Nitrogen and CO2 services. Along with the advantages of using Nitrogen and CO2 in stimulation work, major advances have been made in pumping equipment, storage, and safety measures.

By 1981, more than 800,000 treatments had been performed. As of 1988, this has grown to exceed 1 million. About 35 to 40% of all currently drilled wells are hydraulically fractured. Conservative estimates suggest that approximately 75% of wells that have been fractured have increased production. Many fields exist today because of the use of hydraulic fracturing techniques. About 25 to 30% of total U.S. reserves have been made economically producible by the process. Fracturing is responsible for increasing North America’s oil reserves by 8 billion barrels. In addition to creating reservoir fractures for improving well productivity, hydraulic

© 2005, Halliburton

Figure 1.17 - Large frac-acid job

1 • 15

Stimulation I

Introduction to Stimulation

Halliburton Energy Services Vision and Mission HES 2003 Vision Statement The Halliburton Energy Services 2003 Vision is to be the undisputed leader in Real Time Reservoir Solutions. The fundamental principles to achieving our vision involve: •

Providing superior value to shareholders and customers

•

Creating a company-wide environment for developing, motivating, and rewarding our people

•

Being the undisputed leader in innovative technology, integrated solutions and health, safety and the environment.

•

Being No. 1 or 2 in core discrete businesses

•

Leveraging Halliburton Company's total capability

Production Enhancement Vision and Guiding Principles The leader in optimizing well performance through reservoir understanding and integrating intelligent stimulation and completions, we strive to •

Demonstrate the greatest value created

•

Make it easy to do business with HES

•

Consistently provide best-in-class performance

© 2005, Halliburton

1 • 16

Stimulation I

Introduction to Stimulation

HES Mission Statement Our Mission Statement defines our purpose and our beliefs in how we want to achieve our vision by providing "markers or guideposts" to our beliefs as a company. Halliburton Energy Services (HES), a business unit of Halliburton Company, is a global provider of products, services, and solutions to the energy industry. To be successful, HES must focus on the needs of our customers. We are to continually find creative solutions that maximize the economic recovery of the oil and gas reservoir. The means by which we will enable our customers to be successful is by aligning with their goal of reducing the cost of oil and gas produced, through providing reliable, costeffective solutions, delivered by expert personnel with the following values and principles: •

Perform at the highest levels of service quality that exceed our customers’ expectations

•

Believe that all accidents are preventable and strive for an incident-free workplace

•

Recognize that we are responsible for protecting the environment and consistently meeting those responsibilities

•

Continually apply new technology that benefits our customers and distinguishes Halliburton Energy Services from our competitors as a leader in fit for purpose solutions

•

Support a culture of real-time decision-making and speed to ensure responsiveness to our customers’ needs

•

Maintain integrity in all of our actions — always honor our commitments

•

Be flexible and innovative in our business models and recognized as the leading company with whom it is easy to do business

By virtue of our mission and values, Halliburton Energy Services expects to be the most valued provider of solutions to our customers. And because we are successful in meeting our customers’ needs and good business practices, we expect to deliver superior financial performance to our shareholders. We can only accomplish this with the efforts and participation of our employees; therefore, we must commit to invest in our people to promote a climate of enthusiasm, teamwork, and challenge which attracts, motivates and retains superior personnel and rewards performance.

© 2005, Halliburton

1 • 17

Stimulation I

Introduction to Stimulation

General Safety and Work Guidelines can be hazardous if the way is littered with loose boards, scraps of oil field equipment, nails and scrap iron, or mud-filled holes.

Everyone, at times, hesitates to admit that he or she does not know all there is to know about the job, operation, or machine to which he or she is assigned. Consequently, the supervisor in charge of the job, who is responsible for the safety of the crew, may assume that the worker fully understands the safety rules. So he leaves them alone.

Always wear safety hats and safety shoes on the job. When assembling hammer-up type unions wear safety shields or goggles for the operation. Carefully observe the following precautionary measures:

As a result of this assumption, sooner or later someone is injured, equipment is ruined, or a well is damaged. Every supervisor prefers that workers ask questions about the job--it shows interest and a desire to learn and progress. Remember, no one knows everything, even about his or her work. It is no admission of dumbness or lack of experience to admit “I’m not sure I know how you want this done.”

1. No smoking is allowed on or near the well site. 2. Never wash tools and equipment in flammable mixtures in areas without proper ventilation. 3. Keep all hammers, chisels, punches, etc. properly dressed to eliminate the possibility of steel particles becoming dislodged. Cold chisels and hammers have destroyed the sight of countless numbers of eyes.

Safety begins for the job even before you leave home. A worker who gets plenty of proper rest and nourishment is provided the alertness that is necessary to be a safe worker.

4. Make certain of proper footing when climbing around the equipment. Do not grasp anything for support that is not properly secured.

Get up in plenty of time to thoroughly awaken and clean up before driving to the job. Take enough clothing to comfortably complete the pending job. If it is to be a long job, be certain you have plenty of spare clothes. On the way to the location is a good time to become oriented with the coming operation. Ask questions concerning what is expected of you and the crew on the job. On the way back home it is a good idea to discuss the job. It may reveal mistakes that could have been prevented. It may recall to your mind an unsafe condition, which can be avoided under similar conditions in the future. And it will aid in keeping the driver from becoming drowsy and sleepy through the boredom of a long drive. If the driver does appear to be getting drowsy, it’s time for another coffee break.

6. Before every job, you must have a tailgate safety meeting on location to discuss the job and potential safety hazards while on location. 7. Think the project through before proceeding with any operation around the well site. 8. The most dangerous part of your job is on the roads to and from the field. Ask your Supervisor for special instructions concerning your driving duties. 9. All safety equipment should be carried in its proper place on the vehicle. This equipment should be checked periodically. It is the duty

After arriving at the location and changing to work clothes, clear the way to the equipment site. This preparation is especially important on a new location. Transporting heavy equipment

© 2005, Halliburton

5. Your supervisor is responsible for the safety of the crew. Follow his or her instructions and always seek advice if you do not understand the procedure at hand.

1 • 18

Stimulation I

Introduction to Stimulation

of the operator to know the location of the equipment and its proper operation. In short: •

Be sure you know how to do the job.

•

Be sure you know the hazards of the job and how to protect yourself.

© 2005, Halliburton

1 • 19

•

If you are not sure, ask the advice of your supervisor.

•

Study the rules and regulations in the HES Safety Policy Manual

Stimulation I

Introduction to Stimulation

Stimulation Job Descriptions (Frac/Acid) Operator Assistant •

Assists in rigging up and down of Frac/Acid service line equipment.

•

Assists in assembly and preparation of equipment for installation and service.

•

Assists in the running of a job and in the clean up, repair, and preparation for the next job. Promotes and takes an active part in the Quality Improvement Process.

•

Ensures compliance with Health, Safety, and Environmental (HSE) regulations and guidelines.

•

Drives a truck or other assigned equipment as required. Requires a high school diploma, GED, or equivalent experience. May require a valid Commercial Driver's License.

•

Must have successfully passed company tests or met task guideline requirements.

Service Supervisor

•

•

•

Promotes safety awareness and environmental consciousness, and complies with all applicable safety and environmental procedures and regulations. Works under direct supervision with no experience required. This is the entry-level position into the service operator job family.

•

Coordinates and oversees the Frac/Acid service line work at the well site handling the more complex, hazardous, and/or high profile jobs providing quality service to the customer.

•

Provides the planning necessary for the job including instructions to the crew and equipment used, including dispute resolutions to approved levels.

•

Promotes and takes an active part in the Quality Improvement Process, and ensures that Halliburton Management System (HMS) guidelines are followed.

•

Ensures compliance with HSE regulations and guidelines. Promotes safety awareness and environmental consciousness, and complies with all applicable safety and environmental procedures and regulations.

•

Ensures customer satisfaction with work performed.

•

Coordinates and directs the activities of service operators during the rigging up and rigging down on a location of service line equipment and the assembly and preparation of equipment for installation, running, and service of a job.

•

Coordinates the clean up, repair, and preparation of equipment for the next job.

•

Plans and performs necessary calculations for the total job at the well site as needed.

•

Evaluates individual performance levels of the crew and trains operators to improve their job performance.

Service Operator •

Rigs Frac/Acid service line equipment under direct supervision to provide quality service to the customer.

•

Performs, with limited supervision from the Service Supervisor, in the rigging up and rigging down on a location of service line equipment and in the clean up, repair, and preparation of equipment for the next job.

•

Assembles and prepares, as directed, equipment for installation and service.

•

Promotes and takes an active part in the Quality Improvement Process. Ensures compliance with HSE regulations and guidelines.

•

Promotes safety awareness and environmental consciousness, and complies with all applicable safety and environmental procedures and regulations.

© 2005, Halliburton

1 • 20

Stimulation I

Introduction to Stimulation

•

customer satisfaction for the long term growth and profitability of the NWA.

Requires a high school diploma, GED, or equivalent experience and a valid Commercial Driver's License as required. Demonstrates exceptional skills within the service line and a general understanding of other service functions.

•

Manages processes to ensure job site execution as designed.

•

Follows up job site performance with customer.

•

Maintains MBU performance measures and documents results and best practices. (This classification is available only for North America MBU participants).

Service Leader •

In addition to responsibilities as a Service Supervisor, is also the PSL Mobile Business Unit Leader.

•

Responsible for development and leadership of the Frac/Acid PSL profit center within the NWA.

•

The MBU Leader's emphasis is on personnel development, operational excellence and

© 2005, Halliburton

1 • 21

Stimulation I

Introduction to Stimulation

Oilfield Terms, Slang, and Acronyms forces. Aggregates are stable to normal stirring, shaking, or handling as powder or a suspension. They may be broken by drastic treatment such as ball milling a powder or by shearing a suspension. An essentially inert material of mineral origin having a particle size predominantly greater than 100 mesh, which forms a mortar or concrete when bound together with hardened cement paste.

Sometimes, it may seem that those working in the oilfield are speaking an utterly different language. The oil industry and Halliburton have come up with many terms, slang, and acronyms that you need to know.

Common Oilfield Terms ABANDON- Cease effort to produce oil or gas from a well, plug a depleted formation salvaging all material and equipment.

ALKALINITY- Combines power of a base measured by the maximum number of equivalents of acid with which it can react to form a salt. In water analysis, it represents the carbonates, bi-carbonates, hydroxides, and occasionally the borates, silicates, and phosphates in the water.

ABSOLUTE PERMEABILITY- Measures ease which a fluid will flow through a porous medium. ABSOLUTE VOLUME - Volume per unit mass, reciprocal of absolute density. ACID- Any chemical compound containing hydrogen capable of being replaced by positive elements or radicals to form salts. In terms of the dissociation theory, it is a compound that, on dissociation in solution, yields excess hydrogen ions. Acids lower the pH. Examples of acids or acidic substances are: hydrochloric acid, tannic acid, sodium acid pyrophosphate. Substance that molecules ionize in a water solution to release the hydrogen ion from the constituent element. The strength of an acid is proportional to the concentration of hydrogen ions present. ACIDITY - Relative acid strength of liquids as measured by pH. pH value below 7. See pH.

AMPHOTERIC - Anionic or cationic depending on outside conditions pH for example. ANAEROBIC- Bacteria that do not require free oxygen to thrive. ANHYDRITE- See Calcium Sulfate. Anhydrite is often encountered while drilling. It may occur as thin stringers or massive formations. CaSO4.

ACIDIZING- The practice of applying acids to the walls of oils and gas wells to remove any material which obstructs the entrance of fluids. Also used in carbonate formations, such as limestone, to increase porosity.

ANIONIC- Refers to any anion (atom or chemical group bearing a negative electrical charge). It is used specifically to describe certain surfactants. An anionic surfactant ionizes to produce a cation (positively charged) ion which is usually a metallic ion such as sodium. When a cation is produced through ionization, an anion must also be produced.

ADDITIVE - Material other than cement and water which is added to cement subsequent to its manufacture to modify its properties. AERATE- Intimately admixing water and air.

ANNULUS (ANNULAR SPACE) - The space surrounding pipe suspended in the well bore.

AGGREGATE- A group of two or more individual particles held together by strong

© 2005, Halliburton

AMBIENT- We use this term to describe temperature. Strictly speaking, the term is defined as “completely surrounding.” Ambient temperature would then be the temperature of the air surrounding us. We stretch this definition a little and refer to pumping fluids at ambient temperature. We mean we don’t heat or cool the fluid, but use it just like it is in the tank.

1 • 22

Stimulation I

Introduction to Stimulation

BASE - Compound of metal, or a metal-like group, with hydrogen and oxygen in the proportion to form an OH radical, which ionizes in aqueous solution to yield excess hydroxyl ions. Bases are formed when metallic oxides react with water. Bases increase the pH. Examples are caustic soda and lime.

The outer wall of the annulus may be an open hole or it may be larger pipe. API- American Petroleum Institute. API GRAVITY- The gravity (weight per unit volume) of crude oil or other related fluids as measured by a system recommended by the American Petroleum Institute. It is related to specific gravity by the following formula:

BASICITY - pH value above 7, ability to neutralize or accept protons from acids.

Deg API = 141.5_- 131.5 sp gr 60°F/60°F

BED - Specific layer of earth or rock material in contrast to other layers of earth or rock of different material lying above, below, or adjacent to the bed in reference.

APPARENT VISCOSITY- The viscosity a fluid appears to have on a given instrument at a stated rate of shear. It is a function of the plastic viscosity and the yield point. The apparent viscosity in centipoises, as determined by the direct-indicating viscometer (which see), is equal to 1/2 the 600-rpm reading. See also Viscosity, Plastic Viscosity and Yield Point. In a Newtonian fluid, the apparent viscosity is numerically equal to the plastic viscosity.

BENTONITE- A highly plastic, highly colloidal clay, largely made up of the mineral, montmorillonite, plastic, colloidal clay, largely made up of the mineral sodium montmorillonite, a hydrated aluminum silicate. Used in drilling fluids, bentonite has a yield in excess of 85 bbl/ton. The generic term “bentonite” is neither an exact mineralogical name, nor is the clay of definite mineralogical composition.

AQUEOUS - Used to describe fluids prepared from water. Usually used to distinguish from hydrocarbon fluid. An aqueous fluid may be plain fresh water, or it may have a great number of additives, which give it properties much different from plain water. Examples are salt water of various weights, HCL, KCL water, formic and acetic acids.

BICARB - See Sodium Bicarbonate. BIOCIDE- Used interchangeably with the word bactericide. “Bio” means life and “cide” means kill. BLOCKS, CROWN AND TRAVELING- The block and tackle on a rig that raises and lowers the drill string.

AROMATIC- Describes those hydrocarbons that have carbon chains bent and connected to form a ring or cycle. Aromatic hydrocarbons are sometimes called “cyclic” hydrocarbons. Many of these compounds, as the name implies, have a fragrant or spicy odor. Xylene bottoms are a mixture of aromatic compounds including xylene, benzene and toluene. A solid aromatic hydrocarbon which is commonly used is napthalene or mothballs.

BLEED OFF OR BLEED DOWN- Reduce pressure by letting oil or gas escape at a low rate. BLOOIE LINE- Flow line for air or gas drilling. BLOWOUT - Uncontrolled escape of drilling fluid, gas, oil, or water from the well caused by the formation pressure being greater than the hydrostatic head of the fluid in the hole.

BACK-OFF- Unscrew.

BLOWOUT PREVENTER- A device attached immediately above the casing, which can be closed and shut off the hole should a blowout occur.

BACK PRESSURE - Pressure resulting from restriction of full natural flow of oil or gas. BACTERIA- The simplest form of animal life. BACTERICIDE - Agent capable of destroying bacteria.

BOTTOM-HOLE PRESSURE- The pressure at the bottom of a well.

BARREL - A volumetric unit of measure used in the petroleum industry consisting of 42 gal.

© 2005, Halliburton

1 • 23

Stimulation I

Introduction to Stimulation

BOTTOMHOLE TREATING PRESSUREThe pressure in the wellbore at the perforations required to extend the fracture while overcoming closure pressure, fracture friction, and rock strength. See Fracture Extension Pressure. BREAKDOWN PRESSURE- The pressure observed from a well when the formation is fractured for the first time. This data is also useful in the drilling and cementing processes.

CALCIUM HYDROXIDE - Ca(OH)2. An active ingredient of slaked lime also the main constituent in cement (when wet). This material is referred to as “lime” in field terminology. CATALYST - Chemical useful for enhancing the rate at which a chemical reaction takes place while undergoing no chemical change itself.

BREAKER- Chemicals that function by degrading the long chain polymer into shorter chains with controlled and predictable viscosity decrease.

CATIONIC- Refers to any cation (atom or chemical group bearing a positive electrical charge). It is used specifically to describe certain surfactants. A cationic surfactant ionizes to produce an anion (negatively charged ion) which is usually a non-metallic ion such as chloride or sulfate. When an anion is produced through ionization, a cation must also be produced.

BRINE- Water saturated with or containing a high concentration of common salt (sodium chloride); hence, any strong saline solution containing such other salts as calcium chloride, zinc chloride, calcium nitrate, etc. BUBBLE POINT- The pressure above which a hydrocarbon fluid exists only as a liquid; synonymous with saturation pressure.

CAUSTIC OR CAUSTIC SODA- See Sodium Hydroxide. CENTIPOISE (CP) - A unit of viscosity equal to 0.01 poise. A poise equals 1 g per metersecond, and a centipoise is 1 g centimetersecond. The viscosity of water at 20°C is 1.005 cp (1 cp = 0.000672 lb/ft-sec).

BUFFER - Substance or mixture capable in solution of neutralizing both acids and bases, thereby maintaining the original hydrogen-ion concentration. BY-PASS- Usually refers to a pipe connection around a valve or other control mechanism. A by-pass is installed in such cases to permit passage of fluid through the line while adjustments or repairs are made on the control, which is by-passed.

CHERT - Quarzitic rock with hardness equal to or harder than flint. CHRISTMAS TREE- A term applied to the valves and fittings assembled at the top of a well to control the flow of the oil or gas.

CAKE CONSISTENCY- According to API RP 13B, such notations as “hard,” “soft,” “tough,” “rubbery,” “firm,” etc., may be used to convey some idea of cake consistency.

CIRCULATE- To cycle drilling fluid through drill pipe and well bore while drilling operations are temporarily suspended. This is done to condition the drilling fluid and the well bore before hoisting the drill pipe and to obtain cuttings from the bottom of the well before drilling proceeds. Circulation of the drilling fluid while drilling is suspended is usually necessary to prevent drill pipe from becoming stuck.

CAKE THICKNESS- The measurement of the thickness of the filter cake deposited by a drilling fluid against a porous medium, most often following the standard API filtration test. Cake thickness is usually reported in 32nd of an inch. See Filter Cake and Wall Cake. CALCIUM CARBONATE - CaCO3. An insoluble calcium salt sometimes used as a weighting material (limestone, oyster shell, etc.), in specialized drilling fluids. It is also used as a unit and/or standard to report hardness.

© 2005, Halliburton

CALCIUM CHLORIDE - CaC12. A very soluble calcium salt sometimes added to drilling fluids to impart special properties, but primarily to increase the density of the fluid phase.

1 • 24

CLAY- A hydrated aluminum silicate. Clays are components of soils in varying percentages. Some types swell with absorption of water. Various types are: kaolinite, smectite, illite, chlorite and mixed-layer. A plastic, soft, variously colored earth, commonly a hydrous

Stimulation I

Introduction to Stimulation

silicate of alumina, formed by the decomposition of feldspar and other aluminum silicates. See also Attapulgite, Bentonite, High Yield, Low Yield, and Natural Clays. Clay minerals are essentially insoluble in water but disperse under hydration, shearing forces such as grinding, velocity effects, etc., into the extremely small particles varying from submicron to 100-micron sizes. CLAY CONTROL ADDITIVES- Chemical additives used to minimize the possibility of clay crystals breaking loose and migrating using ionic charge and organic polymer. CLEAN VOLUME- Volume of fracturing fluid before adding proppant. CLOSURE PRESSURE- There is two uses of this term: (1) The minimum hydraulic pressure required to hold a fracture open. This pressure is obtained from either minifracturing or microfracturing data. The closure pressure is the same Closure Pressure as the least principal rock stress. (2) This term is also used to refer to “closure stress,” or the stress the formation applies to the proppant bed after fracturing. Note: These two uses of this term should not be confused.

CORROSION INHIBITOR INTENSIFIERAn additive that cannot be considered as an inhibitor when used alone but has the ability to improve the effectiveness of conventional organic inhibitors when used with them. CRATER (TO CRATER) - Term meaning the hole is caving in. To crater refers to the results that sometime accompany a violent blowout during which the surface surrounding the well bore falls into a large hole blown in the earth by the force of escaping gas, oil, and water. The crater sometimes covers an area of several acres and reaches a depth of several hundred feet. CRITICAL POINT - The pressure and temperature where all lines of constant liquid content coverage for a given hydrocarbon mixture; the pressure and temperature at which all intensive properties of the vapor and liquid are the same.

CLOSURE STRESS- Stress applied to the proppant bed after fracturing. Closure stress is not equal to closure pressure. Closure stress is equal to instantaneous shut-in pressure minus bottomhole flowing pressure. Consequently, closure stress in the proppant bed is a function of time.COLLAR - Pipe coupling threaded on the inside.

CRITICAL PRESSURE- The point at which a constant pressure occurs indicating a reduction in the fracture extension rate (as defined by Nolte). CROSSLINKING - Union of high-polymer molecules by a system involving primary chemical bonds. CROWN BLOCK - Sheaves and supporting beams on top of derrick. D’ARCY - Unit of permeability. A porous medium has a permeability of 1 darcy when a pressure of 1 atm on a sample 1 cm long and 1 sq cm in cross section will force a liquid of 1-cp viscosity through the sample at the rate of 1 cc per sec.

COMING OUT OF HOLE - Withdrawing of the drill pipe from the well bore. This withdrawal is necessary to change the bit, or change from bit to core barrel, to prepare for a drill stem test, and for other reasons.

D’ARCY’S LAW- The rate of flow of a homogeneous fluid through a porous medium is proportional to the pressure of hydraulic gradient and to the cross-sectional area normal to the direction of flow and inversely proportional to the viscosity of the fluid.

CONDENSATE- Hydrocarbons which are in the gaseous state under reservoir conditions but which become liquid either in passage up the hole or at the surface. CONDUCTIVITY - See Fracture Conductivity.

© 2005, Halliburton

CORROSION- The adverse chemical alteration on a metal or the eating away of the metal by air, moisture, or chemicals; usually an oxide is formed. Deterioration of metal due to reaction with the environment.

1 • 25

Stimulation I

Introduction to Stimulation

change alone. Natural gas that is produced with liquids; also a gas that has been treated to remove all liquids.

DENSITY- When used in relation to materials such as solids, liquids, or gases, this means the weight of a unit volume of the material. Many types of units are used to measure density. The chemist usually uses grams per cubic centimeter (gm/cc). In the oil patch we may use pounds per cubic foot (lb/cu ft) for solids, pounds per gallon (lb/gal) for liquids and pounds per cubic foot (lb/cu ft) for gases.

DRY HOLE- Somewhat loosely used in oil work, but in general any well that does not produce oil or gas in commercial quantities. A dry hole may flow water, or gas, or may even yield some oil to the pump, but no in commercial quantities.

DIFFERENTIAL ETCHING- The removal of formation during fracturing acidizing in an uneven manner (hills and valleys). Once the formation closes, the area where the most rock was removed can act as permeable flow channels while the other areas act as support to keep these channels open.

ELEVATORS- Latches which secure the drill pipe or casing; attached to the traveling block which raises and lowers the pipe from the hole. EMULSION- A substantially permanent heterogeneous liquid mixture of two or more liquids that do not normally dissolve in each other but which are held in suspension or dispersion, one in the other, by mechanical agitation or, more frequently, by adding small amounts of substances known as emulsifiers. Emulsions may be mechanical, chemical, or a combination of the two. They may be oil-inwater or water-in-oil types.

DIFFERENTIAL PRESSURE -Difference in pressure between the hydrostatic head of the drilling-fluid column and the formation pressure at any given depth in the hole. It can be positive, zero, or negative with respect to the hydrostatic head. DIFFUSION -Spreading, scattering, or mixing of a material (gas, liquid, or solid).

ENZYME- One of a group of complex organic substances formed in the living cells of plants and animals. They are necessary catalysts for the chemical reactions of biological processes (such as digestion).

DIRTY VOLUME - Volume of fracturing fluid after adding proppant. DOG-LEG - The “elbow” caused by a sharp change of direction in the well bore. Bend in pipe, a ditch, or a well.

FATIGUE - Failure of a metal under repeated loading. FAULT - Geological term denoting a formation break, upward or downward, in the subsurface strata. Faults can significantly affect the area mud and casing programs.

DOPE- Material used on threads of pipe or tubing to lubricate and prevent leakage. DOUBLE- Two lengths or joints of pipe joined together.

FEMALE CONNECTION - Pipe or rod coupling with the threads on the inside.

DRILL-STEM TEST (DST)- A test to determine whether oil and/or gas in commercial quantities has been encountered in the well bore.

FILTER CAKE- The suspended solids that are deposited on a porous medium during the process of filtration. See also Cake Thickness.

DRILL STRING- The string of pipe that extends from the bit to the Kelly, carries the mud down to the bit, and rotates the bit.

FILTRATE - Liquid that is forced through a porous medium during the filtration process. For test, see Fluid Loss.

DRILLING MUD OR FLUID- A circulating fluid used in rotary drilling to perform any or all of various functions required in the drilling operation.

FITTINGS- The small pipes and valves that are used to make up a system of piping.

DRY GAS - Hydrocarbon fluid which exists at a reservoir temperature above its cricondentherm; a gas which cannot be liquefied by pressure

© 2005, Halliburton

1 • 26

FLOCCULATION- Loose association of particles in lightly bonded groups, non-parallel association of clay platelets. In concentrated

Stimulation I

Introduction to Stimulation

filtrates. Asphalt from crude oil will also damage some formations. See Mudding Off.

suspensions, such as drilling fluids, flocculation results in gelation. In some drilling fluids, flocculation may be followed by irreversible precipitation of colloids and certain other substances from the fluid, e.g., red beds.

FORMATION PRESSURE - Pressure at the bottom of a well that is shut in.

FLOORMAN - Member of the drilling crew whose work station is about the derrick floor. On rotary drilling rigs normally there are two floormen on each drilling crew. FLUID FLOW- State of fluid dynamics of a fluid in motion is determined by the type of fluid (e.g., Newtonian, plastic, pseudoplastic, dilatant), the properties of the fluid such as viscosity and density, the geometry of the system, and the velocity. Thus, under a given set of conditions and fluid properties, the fluid flow can be described as plug flow, laminar (called also Newtonian, streamline, parallel, or viscous) flow, or turbulent flow. See terms and Reynolds number. FLUID LOSS- The volume of fluid lost to a permeable material due to the process of filtration. The API fluid loss is the volume of fluid in a filtrate as determined according to the Fluid-Loss Test given in API RP 10B. See Water Loss.

FRACTURE - Cracks and crevices in the formation either inherent or induced. FRACTURE OPENING PRESSURE Pressure required to open an existing fracture. Because this pressure is sometimes close to the closure pressure, these terms are often used synonymously. Since the fracture extension pressure is obtained after the opening pressure, these terms are sometimes used interchangeably. FRACTURING - Application of hydraulic pressure to the reservoir formation to create fractures through which oil or gas may move to the well bore. GAS CONDENSATE - Hydrocarbon fluid which exists at a reservoir temperature above that of the critical point and below cricondentherm of the mixture.

FLUID-LOSS ADDITIVE- An additive used to reduce the fluid loss of cement slurries. Material used to maintain adequate injected fluid within the created fracture and to minimize damage by controlling fluid leak-off. FLUID MOBILITY - Instantaneous ratio of effective permeability for fluid to its viscosity. FOAM- A foam is a two-phase system, similar to an emulsion, where the dispersed phase is a gas or air. Dispersion of a gas in a liquid. FOAMING AGENT - Substance that produces fairly stable bubbles at the air-liquid interface due to agitation, aeration, or ebullition. In air or gas drilling, forming agents are added to run water influx into aerated foam. This is commonly called “mist drilling.” Surface active agent capable of stabilizing a foam.

GAS-OIL RATIO- The number of cubic feet of gas produced with a barrel of oil. GEL - Viscous solution or semi-solid dispersion of a solid in a liquid. The solids may be either natural polymers or synthetic polymers. These solids are composed of fibrous strings of extremely long molecules. The polymer particles swell when placed in a fluid and take part of the fluid into the fibrous structure. This gives the fluid viscosity which may vary from a slight thickening of the fluid to the creation of a rigid gel similar to set gelatin. Gels are clear or translucent. GONE TO WATER- Describes a well in which water production is increasing. GRAVITY, SPECIFIC- The weight of a particular volume of any substance compared to the weight of an equal volume of water at a reference temperature. For gases, air is usually taken as the reference substance, although hydrogen is sometimes used.

FORMATION DAMAGE- Damage to the productivity of a well resulting from invasion into the formation by mud particles or mud

© 2005, Halliburton

FORMATION VOLUME FACTOR Reservoir pore volume occupied by a unit volume of stock-tank oil and its associated gas.

1 • 27

Stimulation I

Introduction to Stimulation

circulating water and mud into a completed well before starting well service operations.

GROSS INTERVAL - Vertical distant between persistent and correlatable log markers above and below the entire reservoir interval.

LAMINAR FLOW- Fluid elements flowing along fixed streamlines which are parallel to the walls of the channel of flow. In laminar flow, the fluid moves in plates or sections with a differential velocity across the front which varies from zero at the wall to a maximum toward the center of flow. Laminar flow is the first stage of flow in a Newtonian fluid; it is the second stage in a Bingham plastic fluid. This type of motion is also called parallel, streamline, or viscous flow. See Plug and Turbulent Flow. Fluid flow where neighboring layers are not mixed.

GUAR GUM- A naturally occurring hydrophilic polysaccharide derived from the seed of guar plant. The gum is chemically classified as a galactomannan. Guar gum slurries made up in clear fresh or brine water possess pseudoplastic flow properties. HYDRATION - Act of a substance to take up water by means of absorption and/or adsorption. HYDROCARBON - Compound consisting only of molecules of hydrogen and carbon. HYDROSTATIC HEAD- The pressure exerted by a column of fluid, usually expressed in pounds per square inch. To determine the hydrostatic head at a given depth in psi, multiply the depth in feet by the density in pounds per gallon by 0.052.

LEAST PRINCIPAL STRESS- The smallest principal stress in an elemental cube with one face oriented normal to the vertical. This stress is also referred to as Horizontal Effective Stress, Horizontal Stress, Closure Pressure or HST.

INHIBITOR (CORROSION) - Any agent which, when added to a system, slows down or prevents a chemical reaction or corrosion. Corrosion inhibitors are used widely in drilling and producing operations to prevent corrosion of metal equipment exposed to hydrogen sulfide, carbon dioxide, oxygen, salt water, etc. Common inhibitors added to drilling fluids are filming amines, chromates, and lime.

LINER- Any string of casing whose top is situated at any point below the surface. LOG - Running account listing a series of events in chronological order. The driller’s log is a tour-to-tour account of progress made in drilling. Electric well log is a record of geological formations which is made by a well logging device. This device operates on the principle of differential resistance of various formations to the transmission of electric current.

INORGANIC- Compounds of earthy or mineral origin such as: water, limestone, dolomite, gypsum, HCl, etc; no carbon compounds are included except cyanides or carbonates.

MALE CONNECTION - Connection with the threads on the outside.

INSTANTANEOUS SHUT-IN PRESSURE (ISIP) - The pressure observed during a hydraulic fracturing operation immediately following the shut-in of the well which negates pressure transients. The difference between the fracture extension pressure and the instantaneous shut-in pressure is the frictional pressure drop across the perforations to the fracture tip. KELLY OR KELLY JOINT - Heavy square pipe or other configuration that works through a like hole in the rotary table and rotates the drill stem. KILLING A WELL - Bringing a well under control that is blowing out. A procedure of

© 2005, Halliburton

MATRIX FLOW - Flow of fluids through the permeable formation. MINI-FRACTURING- A series of tests performed to obtain important information pertinent to the design of the main fracturing job. These tests include a step rate test, a pumpin, flow-back test and a pressure decline test. These tests yield the fracture extension pressure, the closure pressure, the instantaneous shut-in pressure, the opening pressure, the closure time, and the fluid loss coefficient. Further analysis yields the fracture width and the fracture length. MISCIBLE - Solubility of one liquid in another. When a solid dissolves in a liquid, we

1 • 28

Stimulation I

Introduction to Stimulation

NONIONIC- Refers to surfactants which do not ionize and to molecules which neither have positive nor negative charges. They have oilsoluble and water- soluble ends and the wettability characteristics are related to the relative sizes of these ends. Many nonionics will water wet both limestone and sand. They are often blended with anionics or cationics.

say it is soluble in the liquid, as salt is soluble in water. When speaking of liquids, we say that they are immiscible, partially miscible, totally miscible, or miscible in all proportions. MONOMER - Simple molecules that join together to form a polymer are known as monomers and their union is called polymerization. k-TROLtm is pumped into a well as a monomer and polymerizes in the formation to form a polymer.

NON-NEWTONIAN FLUIDS- Fluids that the apparent viscosity changes with agitation or pump rate, for example, gels, emulsions, polymers, mayonnaise. These are fluids that experience apparent viscosity changes with agitation or pump rate. Examples are gels, emulsions or polymers.

MONTMORILLONITE - Clay mineral commonly used as an additive to drilling muds. Sodium montmorillonite is the main constituent in bentonite. The structure of montmorillonite is characterized by a form that consists of a thin platey-type sheet with the width and breadth indefinite, and thickness that of the molecule. The unit thickness of the molecule consists of three layers. Attached to the surface are ions that are replaceable. Calcium montmorillonite is the main constituent in low-yield clays.

OFFSET WELL- Well drilled near another one.

MUD- A water- or oil-base drilling fluid whose properties have been altered by solids, commercial and/or native, dissolved and/or suspended. Used for circulating out cuttings and many other functions while drilling a well. Mud is the term most commonly given to drilling fluids (which see). MUD PIT - Earthen or steel storage facilities for the surface mud system. Mud pits which vary in volume and number are of two types: circulating and reserve. Mud testing and conditioning is normally done in the circulating pit system.

OIL FIELDS - Area where oil is found. Loosely defined term referring to an area in which one or more separate pools or reservoirs may be found. OPEN HOLE- The uncased part of the well.

NET PRESSURE- The bottomhole treating pressure minus closure pressure. The net pressure acts to propagate a fracture.

OPERATOR- The person, whether proprietor or lessee, actually operating a mine or oil well or lease.

NEUTRALIZATION - Reaction in which the hydrogen ion of an acid and the hydroxyl ion of a base unite to form water, the other ionic product being a salt.

OPERATING PRESSURE- The pressure at which a line or system is operating at any given time.

NEWTONIAN FLUID- Fluids with the same apparent viscosity irregardless of the pump rate or agitation, for example, water, oil, molasses.

ORGANIC - Compounds of carbon or carbon and hydrogen (hydrocarbons). Other elements may be present in the make-up of the compound. Examples are: acetic acid, formic acid, all alcohols, natural gas, propane, and crude oil.

NON-EMULSIFIER - Substance which demulsifies (breaks) emulsions or prevents their formation.

© 2005, Halliburton

OIL-BASED MUD- The term “oil-based mud” is applied to a special type of drilling fluid where oil is the continuous phase and water is the dispersed phase. Oil-based mud contains blown asphalt and usually 1 to 5 percent water emulsified into the system with caustic soda or quick lime and an organic acid. Silicate, salt, and phosphate may also be present. Oil-based muds are differentiated from invert-emulsion muds (both water-in-oil emulsions) by the amounts of water used, method of controlling viscosity and thixotropic properties, well-building materials, and fluid loss.

1 • 29

Stimulation I

Introduction to Stimulation

PLASTIC VISCOSITY- Plastic viscosity is a measure of the internal resistance to fluid flow attributable to the amount, type, and size of solids present in a given fluid. It is expressed as the number of dynes per sq cm of tangential shearing force in excess of the Bingham yield value that will induce a unit rate of shear. This value, expressed in centipoises, is proportional to the slope of the consistency curve determined in the region of laminar flow for materials obeying Bingham’s law of Plastic Flow. When using the direct-indicating viscometer, the plastic viscosity is found by subtracting the 300rpm reading from the 600-rpm reading.

OXIDATION- Originally meant the combination of oxygen with some substance. Now any chemical change in which the valence or oxidation state of an element is increased is referred to as oxidation. Oxidation is always accompanied by reduction; that is, when the valence of one element is increased, the valence of another is decreased. An example of oxidation involving a combination with oxygen is that when natural gas and butane burn, they combine with oxygen from the air to form carbon dioxide and water. PAY ZONE OR PAY FORMATIONFormation drilled into that contains oil and/or gas in commercial quantities. PERMEABILITY - Property of a solid medium which allows a fluid to flow through its interconnected pore network. Unit of measurement is the darcy or millicarcy (0.001 darcy). Normal permeability is a measure of ability of a rock to transmit a one-phase fluid under conditions of laminar flow. pH- An abbreviation for potential hydrogen ion. The pH numbers range from 0 to 14, with 7 being neutral, and are indices of the acidity (below 7) or alkalinity (above 7) of the fluid.

PLUG FLOW - Movement of a material as a unit without shearing within the mass. Plug flow is the first type of flow exhibited by a plastic fluid after overcoming the initial force required to produce flow. POLYMER - Substance formed by the union of two or more molecules of the same kind linked end to end into another compound having the same elements in the same proportion but a higher molecular weight and different physical properties, e.g., paraformaldehyde. See Copolymer. The number of simple molecules that unite to form a polymer molecule can be as great as hundreds or thousands. Synthetic polymers we use are such materials as the FR compounds, HYG-1 and HYG-2 (gelling agents for HY-GEL and LOGEL) and the PVC pipe down at the acid terminal. A substance, often synthetic, composed of giant molecules that have been formed by the union of a considerable number of simple molecules with one another. The chemical units occur in a repeating fashion. The number of simple molecules that unite to form a polymer molecule can be as great as hundreds of thousands.

PIG- A scraping tool forced through a flow line or pipe line to clean out wax or other deposits. See Rabbit. PLASTIC FLUID - Complex, non-Newtonian fluid which shear force is not proportional to the shear rate. A definite pressure is required to start and maintain movement of the fluid. Plug flow is the initial type of flow and only occurs in plastic fluids. Most drilling muds are plastic fluids. The yield point as determined by directindicating viscometer is in excess of zero. PLASTICITY- The property possessed by some solids, particularly clays and clay slurries, of changing shape or flowing under applied stress without developing shear planes or fractures. Such bodies have yield points, and stress must be applied before movement begins. Beyond the yield point, the rate of movement is proportional to the stress applied, but ceases when the stress is removed. See Fluid.

© 2005, Halliburton

PLUG BACK - To seal off the bottom section of a well bore to prevent the inflow of fluid from that portion of the hole. This permits the inflow of oil and gas from the formations above the section so sealed off, without contamination of fluids below that depth.

POROSITY- Absolute porosity refers to the total amount of pore space in a rock, regardless of whether or not that space is accessible to fluid penetration. Effective porosity refers to the

1 • 30

Stimulation I

Introduction to Stimulation

consistency decreases instantaneously with increasing rate of shear until at a given point the viscosity becomes constant. The yield point is determined by direct-indicating viscometer is positive, the same as in Bingham plastic fluids; however, the true yield point is zero. An example of a pseudoplastic fluid is guar gum in fresh or salt water.

amount of connected pore spaces, i.e., the space available to fluid penetration. See Permeability. POTASSIUM- One of the alkali metal elements with a valence of 1 and an atomic weight of about 39. Potassium compounds, most commonly potassium hydroxide (KOH) are sometimes added to drilling fluids to impart special properties, usually inhibition.

PUDDLING- In cement evaluation work, the term applies to agitation of cement slurry in molds with a rod, to remove any trapped air bubbles. In field practice, the term has been used to denote the reciprocation or rotation of the casing during or after a cementing operation.

POUR POINT - Lowest temperature at which a liquid will flow when a test container (like a test tube) is tilted. PPM or PARTS PER MILLION- Unit weight of solute per million unit weights of solution (solute plus solvent), corresponding to weightpercent except that the basis is a million instead of a hundred. The results of standard API titrations of chloride, hardness, etc, are correctly expressed in milligrams (mg) of unknown per liter but not in ppm. At low concentrations, mg/l is about numerically equal to ppm. PRECIPITATE - Material that separates out of solution or slurry as a solid. Precipitation of solids in a drilling fluid may follow flocculation or coagulation, such as the dispersed red-bed clays upon addition of a flocculation agent to the fluid. An insoluble solid substance produced as a result of a chemical reaction. PRESSURE - Force per unit area. Bottomhole Circulating Pressure - Pressure at the bottom of a well during circulation of any fluid. It is equal to the hydrostatic head plus the annular friction loss required to pump fluid to the surface plus any back pressure held at the surface.

PUMP-IN/SHUT-IN TEST- See Pressure Decline Test. PUMPING TIME- Synonymous with cementing time except in those instances where a volume of cement slurry is premixed prior to displacement in a well. In this instance, the pumping time will be total cementing time minus mixing time. RATE OF SHEAR - Rate at which an action, resulting from applied forces, causes or tends to cause two adjacent parts of a body to slide relatively to each other in a direction parallel to their plane of contact. Commonly given in rpm.

Bottom Hole Static Pressure - The pressure at the bottom of a well after the well is shut-in long enough to reflect ambient formation pressure.

RELIEF VALVE- A valve that will open automatically when pressure gets to high.

Circulating Pressure - The pressure at a specified depth required to circulate a fluid in a well at a given rate.

RESERVOIR - Each separate, unconnected body of producing formation. RESISTIVITY - Electrical resistance offered to the passage of a current, expressed in ohmmeters; the reciprocal of conductivity. Freshwater muds are usually characterized by high resistivity, salt-water muds by a low resistivity.

Surface Pressure - The pressure measured at the wellhead. PSEUDOPLASTIC FLUID - Complex nonNewtonian fluid that does not possess thixotropy. A pressure or force in excess of zero will start fluid flow. The apparent viscosity or

© 2005, Halliburton

PUMP-IN/FLOWBACK TEST- A test in the minifracturing series with an injection rate varying from a minimum of 3 to 5 barrels per minute up to the proposed injection rate at which the fracturing treatment is to be performed. Flowback rates vary from 0.25 to 1 bbl/min. The closure pressure may be obtained from the pressure inflexion during the flowback portion of this test.

1 • 31

Stimulation I

Introduction to Stimulation

RETROGRADE CONDENSATE - A condensate reservoir fluid with increasing liquid condensation as pressure declines.

SHALE - Fine-grained clay rock with slate-like cleavage, sometimes containing an organic oilyielding substance.

RHEOLOGY - Science that deals with deformation and flow of matter.

SHEAR (SHEARING STRESS) - An action, resulting from applied forces, which causes or tends to cause two contiguous parts of a body to slide relatively to each other in a direction parallel to their plane of contact.

RIGGING UP- Before the work of drilling can be started, but after the derrick has been built, tools and machinery must be installed and a supply of fuel and water must be established. This operation, which in substance is that of getting the rig ready, is conveniently described by the driller’s term “rigging up.”

SILICA FLOUR- Silica (SiO2) ground to a fineness equal to portland cement. The fineness of portland cement is specified in API Std 10A. SKIDDING THE RIG- Moving a rig from the location of a lost or completed hole preparatory to starting a new one. In skidding the rig, the move is accomplished with little or no dismantling of equipment.

RISER - Pipe through which liquid travels upward. ROUGHNECK- A driller’s helper and general all-around worker on a drilling rig.

SLIPS- Wedge-shaped toothed pieces of metal that fit inside a bowl and are used to support tubing or other pipe.

ROUSTABOUT - Laborer who assists the field foreman in the general work about producing oil wells and around the property of the oil company. The roustabout is a semi-skilled laborer in that he requires considerable training to fit him for his work.

SLURRY DENSITY- The density of a cement or fracturing slurry expressed in either pounds per gallon or pounds per cubic foot. Lightweight and heavy-weight slurries are prepared by adding suitable additives to modify slurry density.

SACK- Sack is a weight measure. Cement, bentonite, and barite are marketed in sacks containing amounts as follows:

SODIUM BICARBONATE - NaHCO3. A material used extensively for treating contamination and occasionally other calcium contamination in drilling fluids. It is the halfneutralized sodium salt of carbonic acid.

- Cement- 94 pounds - Sand- 100 pounds - Bentonite- 100 pounds - Barite- 100 pounds

SODIUM CARBONATE - Na2CO3. A material used extensively for treating out various types of calcium contamination. It is commonly called “soda ash.” When sodium carbonate is added to a fluid, it increases the pH of the fluid by hydrolysis. Sodium carbonate can be added to sale (NaCl) water to increase the density of the fluid phase.

SALT- In mud terminology, the term salt is applied to sodium chloride, NaCl. Chemically, the term salt is also applied to any one of a class of similar compounds formed when the acid hydrogen of an acid is partly or wholly replaced by a metal or a metallic radical. Salts are formed by the action of acids on metals, or oxides and hydroxides, directly with ammonia, and in other ways.

SODIUM CHLORIDE - NaCl. Commonly known as salt. Salt may be present in the mud as a contaminant or may be added for any of several reasons. See Salt.

SANDED UP- Clogged by sand entering the well bore with the oil. SETTLING VELOCITY- The velocity at which a particle of particular size, type, specific gravity, and concentration will settle in a fluid of a particular specific gravity and viscosity. It is usually measured in millimeters per second.

© 2005, Halliburton

1 • 32

SODIUM HYDROXIDE - NaOH. Commonly referred to as “caustic” or “caustic soda.” Chemical used primarily to impart a higher pH.

Stimulation I

Introduction to Stimulation

STEP-RATE TEST- A minifracturing test performed to obtain the fracture extension pressure. The test is usually performed by pressuring a well at constant rate increments (example: 0.5, 1.0, 1.5, ...5 barrels per minute) and plotting the maximum pressure at each step vs. the constant rate at each stop. The inflexion point corresponds to the fracture extension pressure.

SOLUBILITY - Amount or percent of a material that dissolves in a certain fluid. For example, if 1.00 grams of a core was ground up and placed in excess HC1, and after several hours the remaining material was filtered out, dried, weighed, and found to weight 0.70 grams, the soluble portion would be 0.30 gram or 30% soluble in HC1. SOUR GAS- Gas that smells bad because of impurities, usually hydrogen sulfide.

STRATIFICATION - Natural layering or lamination usually characteristic of sediments and sedimentary rocks. Stratification is the result of the settling of particles of different sizes and specific gravities.

SPACING- Distance between wells producing from the same pool (usually expressed in terms of acres, e.g., 10-acre spacing). SPECIFIC GRAVITY- Weight of any volume of a material divided by the weight of the same volume of a material taken as a standard. For solids or liquids, the standard is water. For gases, the standard is air. It may also be defined as the ratio of the density of a substance to the density of water or air. We deal mostly with liquids and solids. The density of water is 1 gm/cc or 8.33 lb/gal.

STUCK- Refers to the drill pipe or casing inadvertently becoming fastened in the hole. May occur while drilling is in progress, casing is being run in the hole or while the drill pipe is being hoisted. Frequently results in a fishing job. SUBLIME - Pass directly from a solid to a gaseous state.

SPECIFIC HEAT- Number of calories required to raise 1 g of a substance 1 deg Centigrade. The specific heat of a drilling fluid gives an indication of the fluid’s ability to keep the bit cool for a given circulation rate. SPUDDING- Refers to the acting of hoisting the drill pipe and permitting it to fall freely so that the drill bit strikes the bottom of the well bore with considerable force. This is done to clean the bit of an accumulation of sticky shale that has slowed down the rate of penetration. Careless execution of this operation can result in kinks in the drill pipe and damaged bits. STABBING BOARD -Temporary platform erected in the derrick at an elevation of about 20 to 40 feet above the derrick floor. The derrickman or other crew member works on this board while casing is being run in a well. Derived from the term “to stab” meaning to guide a joint while it is being screwed into another joint or section.

SURFACE TENSION - Forces existing in the surface film of all liquids which tend to contract the volume into a form with the least surface area. This would be a sphere, or a round droplet. The particles in the surface film are inwardly attracted thus resulting in tension. Generally, the force acting within the interface between a liquid and its own vapor, which tends to maintain the area of the surface at a minimum and is expressed in dynes per centimeter. SURFACTANT- In the broadest sense, this can be defined as a “surface active agent.” Or, a chemical which, when added to a liquid, will change the surface tension of the liquid. Practically, we limit the term to those chemicals that lower the surface tension of liquids. A material that raises the surface tension of a liquid we usually call an emulsifier. Materials that tend to concentrate at an interface. Used in

STAND OF PIPE- Two or three or sometimes four joints of pipe fastened together, called a double, thribble, or fourble, respectively.

© 2005, Halliburton

SURFACE PIPE – The first string of casing to be set in a well. The length will vary in different areas from a few hundred feet to three or four thousand feet. Some states require a minimum length to protect fresh-water sands. On some wells it is necessary to set a temporary conductor pipe which should not be confused with surface pipe as described here.

1 • 33

Stimulation I

Introduction to Stimulation

drilling fluids to control the degree of emulsification, aggregation, dispersion, interfacial tension, foaming, defoaming, wetting, etc.

hole. This survey is used to find the location of inflows of water into the hole, where doubt exists as to proper cementing of the casing and for other reasons.

SWABBING- Operation of a lifting device to bring well fluids to the surface when the well does not flow naturally. This is a temporary operation to determine whether or not the well can be made to flow. In the event the well does not flow after being swabbed, it is necessary then to install a pump as a permanent lifting device to bring oil to the surface.

TENSILE STRESS- The perpendicular components of internal stress exert a pull between the two parts of the mass which constitutes a tensile stress. A pull-apart stress. TONGS- A wrench type item used to tighten or loosen drillpipe or casing connections. TOOL PUSHER - Foreman in charge of one or more drilling rigs or supervisor of drilling operations.

SWIVEL - Hose coupling which forms a connection between the slush pumps and the drill string and permits rotation of the drill string.

TORQUE- A measure of the force or effort applied to a shaft, causing it to rotate. On a rotary rig this applies especially to the rotation of the drill stem in its action against the bore of the hole. Torque reduction can usually be accomplished by the addition of various drillingfluid additives.

TALLY - Measure and record length of pipe or tubing. TEARING DOWN - Act of dismantling a rig at the completion of a well and preparing it for moving to the next location.

TOUR- The word which designates the shift of a drilling crew or other oil field workers is pronounced usually as if it were spelled t-o-w-er. The word does not refer to the derrick or tower, as some seem to think, the day tour starts at 7 or 8 in the morning. The evening tour starts at 3 or 4 o’clock in the afternoon. The morning tour starts at 11 p.m. or midnight (sometimes referred to as graveyard tour). The almost universal practice in oil well drilling is to work 8-hour tours or shifts.

TECTONIC- Pertaining to the rock structures and external forms resulting from the deformation of the earth’s crust. TEMPERATURE- The degree of heat usually expressed as degrees Fahrenheit. - Bottomhole Circulating Temperature - The temperature of any fluid at the bottom of the well while it is being circulated. - Bottom Hole Static Temperature - The temperature attained at the bottom of a well after the well is shut-in. See Static Temperature.

TRIP - Pull or run a string of rods or tubing from or into a well.

- Circulating Temperature - The temperature of any fluid at any specified depth in well while it is being circulated, as measured inside casing or drill pipe.

TUBING JOB- The pulling and running of tubing. TURBIDITY - Measure of the resistance of water to the passage of light through it. It is caused by suspended and colloidal matter in the water.

- Static Temperature - The temperature attained at a specified depth in a well after the well is shut-in long enough to reflect the ambient formation temperature.

TURBULENT FLOW - Fluid flow in which the velocity at a given point changes constantly in magnitude and the direction of flow pursues erratic and continually varying courses. Turbulent flow is the second and final stage of flow in a Newtonian fluid; it is the third and

TEMPERATURE STABILITY - Chemical characteristics of a material which determine its resistance to thermal decomposition. TEMPERATURE SURVEY - Operation to determine temperatures at various depths in the

© 2005, Halliburton

1 • 34

Stimulation I

Introduction to Stimulation

final stage in a Bingham plastic fluid. See Critical Velocity and Reynolds Number.

or in some cases by a capillary block of the pores due to surface tension phenomena.

UNDER-REAM - To enlarge a drill hole below the casing.

WET GAS - Gas that carries a lot of liquids with it.

V-DOOR (WINDOW) - An opening in a side of a derrick at the floor level having the form of an inverted V. This opening is opposite the draw-works. It is used as an entry to bring in drill pipe and casing from the pipe rack.

WETTING AGENT- A substance or composition which, when added to a liquid, increases the spreading of the liquid on a surface or the penetration of the liquid into a material. WORKOVER - Perform one or more of a variety of remedial operations on a producing oil well with the hope of restoring or increasing production. Examples of work-over operations are deepening, plugging back, pulling and resetting the liner, squeeze cementing, shooting, and acidizing.

VELOCITY - Time rate of motion in a given direction and sense. It is a measure of the fluid flow and may be expressed in terms of linear velocity, mass velocity, volumetric velocity, etc. Velocity is one of the factors that contribute to the carrying capacity of a drilling fluid.

WORMHOLE - Large, highly conductive channels that result from the matrix reaction of acid with highly reactive sections of the formation. Usually a wormhole starts by enlarging already large permeable vugs or pores and moves forward as it creates additional surface area.

VELOCITY, CRITICAL - Velocity at the transitional point between laminar and turbulent types of fluid flow. This point occurs in the transitional range of Reynolds numbers of approximately 2,000 to 3,000. VISCOMETER (VISCOSIMETER)- An apparatus to determine the viscosity of a fluid or suspension. Viscometers vary considerably in design and methods of testing.

YIELD- A term used to define the quality of clay by describing the number of barrels of a given centipoise slurry that can be made from a ton of the clay. Based on the yield, clays are classified as bentonite, high-yield, low-yield, etc., types of clays. Not related to yield value below. See API RP 13B for procedures.

VISCOSITY- The internal resistance offered by a fluid to flow. This phenomenon is attributable to the attractions between molecules of a liquid, and is a measure of the combined effects of adhesion and cohesion to the effects of suspended particles, and to the liquid environment. The greater this resistance the greater the viscosity. See Apparent and Plastic Viscosity.

YOUNG’S MODULUS - Ratio of stress to strain of a material undergoing elastic strain. ZINC CHLORIDE- ZnCl2. A very soluble salt used to increase the density of water to points more than double that of water. Normally added to a system first saturated with calcium chloride.

VUGS- Natural cavities formed in certain formations due to leaching out of soluble minerals. These cavities are lined with a crystalline material and a composition different from that of the surroundings. The size of a vug may vary from a small pea to a large boulder.

Common Oilfield Acronyms ACE - Automatic Controlled Equipment (formerly HIC) - used in HES pumping equipment

WATER BASE GELLING AGENT - Polymer which thickens or gels water. WATER BLOCK- Reduction of the permeability of a formation caused by the invasion of water into the pores (capillaries). The decrease in permeability can be caused by swelling of clays, thereby shutting off the pores,

© 2005, Halliburton

API - American Petroleum Institute ASME - American Society of Mechanical Engineers BHA - Bottom Hole Assembly

1 • 35

Stimulation I

Introduction to Stimulation

BOM - Bill of Material

HEI - Halliburton Energy Institute - a learning center in Duncan, OK which provides training for employees and customers

BOP - Blow Out Prevention CAST -V - Circumferential Acoustic Scanning Tool - This new generation tool brings higher resolution, precise digital information, and simultaneous measurements for complete acoustic visualization in both open and cased holes.

HIPS - Halliburton Integrated Proposal System HPHT - High Pressure High Temperature HWO - Hydraulic Work Over. Well Control and well maintenance duties. ID - Inside Diameter

CBL - Cement Bond Log

ILAN - Instrument Local Area Network used for UNIPRO communications

CEMS - Computerized Equipment Management System - field system for tracking equipment and repairs

IRJ - Irregular Job Report JLAN - Job Local Area Network used for ARC/ACE communications

CFU - Combination Frac Unit CIBP - Cast Iron Bridge Plug

JSA - Job Safety Analysis

CLAM - Constant Level Additive Mixer

LGC - Liquid Gel Concentrate

CSNG - Compensated Spectral Natural Gamma Ray

LTA - Lost Time Accidents

DAS - Data Acquisition System - used in Coil Tubing, TCCs, COMPUPACs with ACQUIRE

LWD - Logging While Drilling - part of the HDS business

DOT - Department of Transportation - US Federal Agency

M/LWD - Measurement/Logging While Drilling

DST - Drill Stem Test - measure pressures at bottom hole

MBU - Mobile Business Unit - a team with equipment which can deliver products and services to the customer

EMI - Electrical Micro Imaging (EMI(tm)) Service provides cost -effective technology for formation and reservoir evaluation with core like electrical micro -conductivity images of the formation sequence.

MLWD - Measurement While Drilling and Logging While Drilling MRIL - Magnetic Resonance Imaging Log MSDS - Material Safety Data Sheet

EPA - Environmental Protection Agency - US Federal Agency responsible for environmental regulations.

MWD - Measurement While Drilling - system which tracks drill bit location MWD/LWD - Measurement While Drilling/Logging While Drilling

FAR pack - Field Activity Reporting package FOP - Field Operating Profit

N2 - Nitrogen services

FSQC - Field Service Quality Coordinator

NORM - Naturally Occurring Radioactive Material - as it relates to the EPA

FSR - Field Service Representative GIH - Grease Injector Head

NWA - Natural Work Area - A method of dividing up North America into regions which have similar product and service requirements

GOHFER - Grid Oriented Hydraulic Fracture Replicator - Stim -Lab, Inc version of a 3D fracture simulator

OD - Outer Diameter

HEC - Hydroxy Ethyl Cellulose

© 2005, Halliburton

OH - Open Hole

1 • 36

Stimulation I

Introduction to Stimulation

OIP - Operator Interface Panel - used by a person to control a UC OSHA - Occupational Safety and Health Administration - Federal US Agency responsible for worker safety PBR - Polish Bore Receptacle PCI - Pumping Control Interface - a VME box

increasing technical and customer needs on a global basis. Successful completion of the program is expected to lead to promotion of the Participant from entry level (or experienced candidates from within Halliburton) to a revenue producing Service Supervisor in field operations. SSIT - Service Supervisor in Training - is responsible for successful wellsite job execution in a safe and efficient manner. The Service Supervisor's emphasis is on operational excellence and customer satisfaction for long term growth and profitability of the NWA.

PD&C - Product Development & Commercialization PM - Preventive Maintenance - system of checks that ensure equipment is kept at minimum standards to prevent failures during normal operation.

SSSV – Sub-Surface Safety Valve

PO - Purchase Order

StimWin - Stimulation Design Software

POOH - Pull Out Of Hole

T&E - Travel & Entertainment - System of tracking these expenses

PPE - Personal Protective Equipment - used for personal safety in performance of duties coveralls, gloves, eye protection, hearing protection

TA - Technical Advisor

PTA - Plug to Abandon

TC - Team Coordinator -The PSL Team Coordinator Functions as a team leader and coach for the Service Supervisors. The Team coordinator provides personnel development for the MBU Team and champions best practices and process improvements.

QA - Quality Assurance

TCP - Tubing Conveyed Perforating PSL

QC - Quality Control

TD - Target Depth

RIH - Run in Hole

TIMS - Technical Information Management System

PSW - Pumping Services Workstation Realtime data acquisition & display software.

RTO - Real Time Operations - delivery of real time data from wellsite to Halliburton/Client office, typically via use of the Mobile Net satellite system

TTTCP – Tools, Testing and Tubing-Conveyed Perforating. UWI - Unique Well Identifier

SC - Service Coordinator - is a customer focused member of the PSL and Asset Management Team. The Service Coordinator provides technical and operational expertise, champions service excellence, creating customer satisfaction. The Service Coordinator deploys equipment, materials, and personnel with focus on optimizing utilization and profit.

WAN - Wide Area Network WIT - Wellhead Isolation Tool ZI - Zonal Isolation (ZI) is a process used in petroleum well construction which keeps fluids in one permeable zone of the well bore separate from fluids of another zone. Once the well has been drilled and lined with pipe, the connection between the geological formation and the well must be established and assured. Completion includes installing suitable tubing or casing, and cementing this casing, using casing plugs and packers.

SO - Shipping Order SPE - Society of Petroleum Engineers/Society of SSDP - Service Supervisor Development Program is designed to train Supervisors to meet

© 2005, Halliburton

1 • 37

Stimulation I

Introduction to Stimulation

What that really means is, the HMS is what we do, how we do it, who is responsible, how we know we've done it, and how can we make it better.

Common Halliburton Acronyms BU - Business Unit CAPE - Concurrent Art to Production Environment

HPM - Halliburton Performance Management This function includes Market and Business Analysis, Strategic Planning, PSL Marketing and the Product Development and Commercialization Initiative Champion

CBT - Computer-Based Training CEMS - Computerized Equipment Management System - field system for tracking equipment and repairs

HR - Human Resource department

COE - Common Office Environment – An architecture of PCs that standardizes software and hardware throughout the company.

HRD - Human Resource Development -This department drives performance -focused change of our people, processes, and organization, supporting Halliburton’s goal of becoming a high -performing organization. Using the developmental solutions approach, HRD develops and implements specific processes that change and improve performance (processes collectively known as interventions) to support our clients’ business needs

CPI - Correction, Prevention, and Improvement. Halliburton’s quality improvement system. CPS - Completion Products & Services PSL – A reservoir focused set of Completion Solutions including Subsurface Products, Sand Control, Slickline, SEWOP, and Surface Products CT - Coiled Tubing and all its components

HSE - Health, Safety, and Environment. Refers to department policies for ensuring our compliance with HSE regulations.

CVA - Cash Value Added - The CVA for a period is a good estimate of the cash flow generated above or below the investor's requirement for that period. See also NOVA

IS - Integrated Solutions PSL -was established, uniting the best people, technology, products, and equipment to offer oil and gas companies the most effective and profitable solutions to their challenges

EJCS - End of Job Customer Satisfaction Survey F&A - Finance and Administration

IT - Information Technology

FPD - Focused Product Development Process used in Technology Centers

ITP - Integrated Technology Products -The purpose of the Integrated Technology Products Group is to offer solutions with reservoir performance focus; champion the rapid development and introduction of new technologies that cross PSL boundaries; focus on cross -PSL technology delivery as a business; and commercialize multi-PSL solutions based on value creation transfer technology to countries.

FSQC - Field Service Quality Coordinator FSR - Field Service Representative HALCO21 - Halliburton’s team and processes for revolutionizing business processes globally to provide dramatic improvements for Halliburton Company, enabling our success in the 21st Century

JSA - Job Safety Analysis

HEI - Halliburton Energy Institute – the development center in Duncan, Oklahoma, which provides training for employees and customers

KBR - Kellogg Brown and Root – Halliburton’s business unit that provides a full spectrum of services: project development, technology licensing and development, consulting, project management, engineering, procurement, construction, operations and maintenance services.

HMS - Halliburton Management System - is an integrated management system designed to meet operations, quality, health, safety, and environmental management systems needs.

© 2005, Halliburton

1 • 38

Stimulation I

Introduction to Stimulation

KPI - Key Performance Indicator; used as a measure in Service Quality PII

champions service excellence, creating customer satisfaction. The Service Coordinator deploys equipment, materials, and personnel with focus on optimizing use and profit.

L&P - Logging and Perforating PSL MBU - Mobile Business Unit - a team with equipment, which can deliver products and services to the customer

SS - Shared Services - the enabler for change by pulling together the various functions that were common to all our operations under one management structure that exists along side of the other mainstay processes of acquisition and execution. Through this model each Business Unit is able to access the resources necessary to acquire and execute its work, yet gain the efficiencies and synergies available by "sharing" key services between Business Units.

NOVA - Net Operating Value Added NWA - Natural Work Area - A method of dividing up the United States into regions which have similar product and service requirements PD&C - Product Development & Commercialization PE - Production Enhancement PSL

SSDP - Service Supervisor Development Program is designed to train Supervisors to meet increasing technical and customer needs on a global basis. Successful completion of the program is expected to lead to promotion of the Participant from entry level (or experienced candidates from within Halliburton) to a revenue producing Service Supervisor in field operations.

PII - Performance Improvement Initiative Three areas of Performance we can focus on in the delivery of our services, In addition to our financial performance. -Doing the Job Right the First Time by Using Standard Processes and Procedures -Reducing Injuries by Better Management of Risk -Protecting the Environment by Reducing the Amount of Waste Created and Using Environmentally Friendly Operating Practices

SSDS - Sperry-Sun Drilling Services SSIT - Service Supervisor in Training - is responsible for successful wellsite job execution in a safe and efficient manner. The Service Supervisor's emphasis is on operational excellence and customer satisfaction for long term growth and profitability of the NWA.

PPR - People Performance Results - part of the People Performance Management system used to establish goals, provide feedback on performance, assess performance and deliver pay or other incentive based rewards PSL - Product Service Line PSMT - Product Service Management Team

T&E - Travel & Entertainment - System of tracking these expenses

QA - Quality Assurance

TA - Technical Advisor

QC - Quality Control

TC - Team Coordinator -The PSL Team Coordinator functions as a team leader and coach for the Service Supervisors. The Team Coordinator provides personnel development for the MBU Team and champions best practices and process improvements.

RTO - Real Time Operations - delivery of real time data from wellsite to Halliburton/ Client office, typically through use of the Mobile Net satellite system SC - Service Coordinator - is a customerfocused member of the PSL and Asset Management Team. The Service Coordinator provides technical and operational expertise,

© 2005, Halliburton

TTTCP - Tools & Testing and TubingConveyed Perforating PSL

1 • 39

Stimulation I

Introduction to Stimulation

Unit A Quiz Fill in the blanks with one of more words to check your progress in Unit A. 1. Stimulation treatments refer to ____________ and _______________. 2. What are three (3) design requirements necessary for a successful job design? 3. BOP is the acronym for ____________ __________. 4. The first string of casing in a well is called ___________________ ______________________. 5. Who is responsible for the safety of the crew? 6. PTA is the acronym for ____________ __________ __________. 7. The most common method of perforating incorporates __________-__________ __________ . 8. Proppant is used to provide passages for __________ or __________ to flow into the well. Now, look up the suggested answers in the Answer Key.

© 2005, Halliburton

1 • 40

Stimulation I

Introduction to Stimulation

Answer Key Refer to the pages provided as references if you answered any of these items incorrectly, or if you were unsure of your answers. Items from Unit A Quiz

Refer to Page

1. Acidizing/fracturing

5

2. Fluid type, viscosity requirements, fluid rheology, fluid safety, economics of fluid, proppant selection, material availability, experience with local formations, laboratory data on the formation(s).

5

3. Blowout preventer

9

4. Surface Casing

7

5. Service Supervisor

18

6. Plug to abandon

35

7. Shaped-charged explosives

11

8. Oil/gas

13

© 2005, Halliburton

1 • 41

Stimulation I